A number of harvesting machines have been developed utilizing a guidance control or self-steering system that maintains the machine in proper position as it proceeds along a row of plants being harvested. An example of a harvester incorporating a conventional self-steering system is shown in U.S. Pat. No. 4,367,621 to Swetnam et al.
The self-steering system disclosed in the Swetnam et al. patent includes a pair of laterally spaced, outwardly projecting guiding sensors. These sensors sense the presence and/or position of the plants being harvested. More specifically, as the guiding sensors engage the plants steering correction forces are transmitted through a connecting rod to impart movement to the steering crank arm so as to steer the wheels of the harvester. In this way, the harvester is maintained in proper harvesting position as it travels along the entire length of the crop row. Advantageously, the resulting self-steering action frees the harvester operator for other tasks thereby improving overall labor efficiency.
While the self-steering system disclosed in the Swetnam et al. patent provides effective guidance of the harvester along a row, it is not without its disadvantages and may, therefore, be subject to improvement. For example, under certain circumstances steering correction forces may be produced that overcompensate causing the harvester to wander back and forth across the row more than desired. A need is, therefore, identified for a self-steering or guidance control system that is more efficient, providing smoother, (more rapid) response and substantially eliminating wander.